Numerous systems have been proposed for perforating and testing a well with a combination tool string. Examples of such prior proposals are shown in U.S. Pat. Nos. 2,092,337; 2,169,559; 2,330,509 and 2,760,408. In accordance with these disclosures the firing assembly which activates the perforating gun generally is actuated by electrical means, pipe string manipulation, or by dropping an impact bar or "go-devil" through the pipe string. However, electrical actuation generally requires that a wireline be run into the pipe string, which involves additional and time-consuming operations. Systems using pipe string manipulation typically include somewhat complicated mechanical constructions, and can be prematurely activated as the tool string is being run into the well. Systems employing drop bars are not considered to be practical in deviated wells since the bar may not reach bottom. Of course in all cases safety is a primary consideration.
It is the general object of the present invention to provide a new and improved well testing and perforating system wherein the perforating gun is actuated in a safe and reliable manner under controlled well conditions. In the preferred embodiment, actuation is responsive to a predetermined difference in pressures above and below a packer that has been set above the well interval being perforated.